The mechanism that enables enzymes in the soil in certain bacteria to remove carbon monoxide (CO) from the atmosphere has been discovered. The study, conducted by researchers at the University of Milano-Bicocca in collaboration with colleagues at the University of Calabria and the University of Lund, Sweden, has provided a detailed understanding of how these enzymes convert CO into carbon dioxide (CO2). This discovery opens new avenues for mitigating carbon monoxide emissions, leading to benefits for both air quality and climate since this highly toxic gas contributes to the greenhouse effect.
Over the past two decades, several experimental and theoretical studies have been devoted to understanding the process of CO oxidation by a particular enzyme containing molybdenum and copper, referred to as MoCu CO dehydrogenase. The mechanisms that have been hypothesized up to now, however, indicated certain difficulties in the evolution of the product. Thanks to experience gained in previous studies of the system using computational models, the group of researchers composed of Professor Claudio Greco, deputy director of the Department of Environmental and Earth Sciences, Professor Ugo Consentino and researcher Anna Rovaletti of the same department, Professor Giorgio Moro of the Department of Biotechnology and Biosciences, Professor Emilia Sicilia and Dr. Alessandra Gilda Ritacca of the Department of Chemistry and Chemical Technologies, University of Calabria, and Professor Ulf Ryde of the Department of Theoretical Chemistry, Lund University, managed to reproduce, for the first time, a reaction mechanism consistent with the experimental data reported to date. In particular, an explanation was given of how the MoCu CO dehydrogenase enzyme transfers an oxygen atom from water, transforming the monoxide into carbon dioxide. The CO2 produced is used by the same bacteria and is therefore not released into the atmosphere.
The study, entitled “Unraveling the Reaction Mechanism of Mo/Cu CO Dehydrogenase Using QM/MM Calculations” was published in ACS Catalysis (DOI: 10.1021/acscatal.2c01408)
“The atmosphere contains, in small proportions, various gases due to both natural sources and man-made emissions, such as CO,” Professor Greco explains. Enzymes that can transform CO into CO2 are present in several soil microorganisms and can ‘consume’ about 15% of the atmosphere’s carbon monoxide. The discovery of fundamental details about how these enzymes work marks a step toward the ability to design compounds that work in the same way and that could be used both in next-generation sensors for CO detection and for reducing emissions of this gas in industrial processes.”